Stable sabot



July 9, 1957 w. H. ALLAN 2,798,433

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' WALLACE H. ALL-AN ATTORNEYS STABLE SABOT Wallace H. Allan, China Lake, Calif., assignor to the United States of America as represented by the Secretary of the Navy Application June 18, '1953, Seral'No. 362,694

2 Claims. (Cl. 102-933) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental 'purposes without the pay ment of any royalties thereon or therefor.

This invention relates to missiles which are projected, or fired, from guns, and in particular to an aerodynamically stable sabot which is adapted to accelerate a missile to a desired speed when fired from a smooth bore gun.

Sabots have been used in the'past to accelerate missiles to extremely high speeds. To attain the high accelerations necessary to reach such high speeds amissile should have a relatvely low sectional density (mass divided by cross-sectional area) while in the bore. However, after leaving the bore, a missile should have a relatvely high sectional density to minimize the reduction in speed due to aerodynamic drag. A sabot acts to increase the muzzle velocity of a missleby providing the desi'able relatvely low sectional density while the sabot and missile are in the gun bore. After the sabot and missile leave the bore, the missile, which by itself has a relatvely high sectional density, separates from the sabot.

In recent years sabots have been used to accelerate fin stabilized missiles, ,or scale models of missiles, to controlled velocities so that aeroballistic measurements of the missiles could be made. Previously known sabots have functioned correctly while they are in the gun bore; however, after leaving the bore and separating from the missiles the sabots have tumbled so that their trajectories Were erratic and unpredictabl. Other sabots have been designed to break apart after leaving the gun -bo`re,`however, the Components of this typeof sa'bot likewse have erratic trajectories. The unpredictable behavior of sabots after leaving the gun bore has been a major factor in preventing their use as a weapon. In experimental work sabots can be used, but previously known types have required some means for stopping the sabots before they do possible harm.

lt is, therefore, an object of this invention to provide a sabot which is aerodynamically stable so that it follows a predictable trajectory after leaving the gun bore.

It is a further object of this invention to provide an aerodynamically stable sabot suitable for use in a smooth bore gun.

Other objects and many of the attendant advantages of this invention will be readily apprecated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Figl l is a broken away sectional view of a gun barrel with a sabot supporting a missile, which is partly broken away, therein;

Fig. 2 is a sectional view taken along line 2--2 of Fig. 1;

Fig. 3 is a broken away sectional view of a modified form of the invention;

Fig. 4 is a side elevation of Fig. 2 as viewed in the direction of the arrow 4 in Fig. 2; and

States Parent 2',798,43 Patented `luly 9, 1957 Fig. 5 is an elevation of one form of sealing n'ng which may be used with the sabot illustrated in Fig. 3.

Aerodynamically stable sabot 10 has a nose portion 12, a tail portion 14 and a connecting portion 16. The nose portion 12 in the modification illustrated in Fig. 2 is formed from two parts 18 and 20 which are threaded together. The forward portion of part 18 has formed therein a bore 22 and a plurality of slots 24 in which the base and fins 28 of missile 30 are adapted to fit. The number and arrangement of slots 24 can be varied to correspond with the number and arrangement of the fins of missile 30. Another way in which missile 30 can be supported by sabot 10, for example, is by locatng a probe on the forward part 18 of nose portion 12 and by providing the base of missile 30 with a bore into which the probe may be inserted.

Bore 22 and slots 24 are designed to properly support missile 30 within bore 32 of smooth gun barrel 34, and to prevent relative movement of the missile transversely of the longitudinal axis of bore 32. The connection between sabot 10 and missile 30 is such, however, that sabot 10 readily separates from missile 30 after the sabot and missile leave bore 32.

When parts 18 and 20 of nose portion 12 are assernbled, groove 36 is formed therebetween and an annular scaling ring 38, of copper or the like material, is located within groove 36. Orifices 40 provide communication between groove 36 and the high pressure gases behind nose portion 12 of sabot 10.

Tail portion 14 is a hollow 'cylinder having the forward part of its outer surface 42 rounded, or tapered, to facilitate loading sabot 10 in the barrel. The outer surface of tail portion 14 constitutes an aerodynamic stabilizing surface. Connecting portion 16 is also a hollow cylinder and is illustrated as being made integrally with tail por-' tion 14 and the rear part 20 of nose portion 12. Connecting portion 16 is provided with a plurality of openings 44 which have the function of lghtening connecting portion 16, of preventing connecting portion 16 from expanding so that parts of sabot 10 can seize the Wall of bore 32, and of permtting high pressure gas to exert force on gas scaling ring 38 located in groove 36. The action of the gas on ring 38 is to force the ring against the wall of bore 32.

For stable flights the center of gravity of sabot 10 should be as far forward of the geometric center of the sabot as it is possible to locate it. To aid in this,-forward portion 18 of nose portion 12 can be made of a relatvely dense material such as 'steel while tail portion 14, connecting portion 16, and the rear part 20 of nose portion 12 is made of a relatvely light material such as alnminum.

The overall outside diameter of nose portion 12 and tail portion 14 are made substantially equal to each other and slightly less than the internal diameter of bore 32. As a result of this Construction there is substantially no oscillation, or sway, of sabot 10 as it is accelerated down bore 32 of gun barrel 34. The diameter of connecting portion 16 is less than the maximum diameter of the nose and tail portions 12 and 14. The magnitude of the difierence is a matter of choice.

In Fig. 3 a second modification of the invention, is illustrated. Nose portion 112 is made integral with connectng portion 116 with the result that the sabot may be cast in one piece and made of a single material. Groove 136 is formed around nose portion 112. Because of the integral Construction of nose portion 112, it is mpossible to use an integral copper scaling ring such as is used in the sabot illustrated in Fig. 2, therefore, splt scaling ring 138, illustrated in Fig. S, may be used. Orifices 140 provide communication between groove 136 and the high pressure gases behind the nose portion 112 of the sabot to force the scaling ring 138 against the wall of bore 32. The` other details of Construction of the modification iliustratecl in Fig. 3 are similar to those used in the modification illustrated in Fig. 2.

In operation, the base of missile 3@ is placed in bore 22 of forward part 18 of nose portion 12 of sabot The sabot and missile are then placed in bore 32 of gun barrel 34, and a charge of powder, which is not illustrated, V

is located behind sabot 10. After the breech of the gun,

` 1 groove, orices communicatng the interier of the groove with the real' of said sabot for conducting high pressure gases at the rear of the sabot into the groove to expand the sealing ring located in the groove so' that said ring engages the inner wall of the s mooth bore gun to pre vent communication between the fear and the front of the missile while said missile is traveling within the gun, the tail portion being a hollow cylinder, the outer surfacebeing curved to constitute an aerodynamic stabilizer, the connecting portion being a hollow 'cylinder integral with the tail portion and the rear part of the nose portion,

. a plurality of openings formed in said connectng portion,

be omitted when sabots as dsclosed herein are used 'to After sabot 10 and missile 30 leave bore 32, the greater aerodynamic drag of sabot 12 causes it to separate and lag behind missle 30. The location of the center of gravity of sabot 10 together with the stabilizing influence of tail portion 14 gives the sabot suflicent stability to to preventerratic fl ght. When the sabot is used to obtain aeroballistic measurements of a missile, the sabot follows the missile through the experimental range without endangering personnel or equipment. If the sabot is used to accelerate a war Weapon, the sabot has suicient range to clear friendly personnel and equipment.

V/hile the subject of this invention has been described as being useful primarily as a sabot, it could also serve as the missile which is projected from a smooth bore gun or the like.

Obviously many modifications and variations of the' present invention are possible in the light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be praeticed otherwise than as specifically described.

What I claim is:

l. An aerodynamically stable sabot adapted to be fired from a smooth bore gun conprising a nose portion, a tail portion and a connecting portion, the maximum external diameters of the nose and tail portions being substantially equal to each other and slightly less than the internal diameter of the gun bore, the nose portion being formed of two parts, the forward part being made from a relatively dense material and having formed therein a bore and a plurality of slots adapted to support the base and fins of a missile, a groove formed between the two parts of the nose, an expendable gas sealing ring located in said the overall external diameter of said eonnecting portion being less than the said maximum external diameter-s of the nose and tail portions, and the rear part of the nose being made of a less dense material than that from which the forward part of the nose is made.

. 2. An aerodynamically stable sabot adapted to be fired from a smooth bore gun comprising a nose portion, a tail portion and a connecting portion, the maximum external diameters of the nose and tail portions being substantially equal to each other and slightly less 'than the internal diameter of the gun bore, the nose portion being a substan- .tially solid cylinder provided with an annular groove, the

forward part of the nose portion having` formed therein a bore and a plurality of slots adapted to support the base and fins of a missile, an expendable split ring in said annular groove, a plurality of orfices communicating the interior of the grooves with the rear of the sabot for conducting high pressure gases at the rear of the sabot into the annular groove to expand the split ring in said groovc to seal the space between the exterior of the nose portion of the sabot and the nner wall of the bore of the gun While the sabot is traveling within the bore of the gun, the tail portion being a hollow cyiinder, the outer surface being curved to constitute an aerodynamic stabilizer, the connecting portion'being a hollow cylinder integral with the tail and nose portions, a plurality of l openings formed through said connecting portion, the external diameter of the` connecting portion being less than the maximum external diameter of the nose and tal portions.

References Cited in the file of this patent UNITED STATES PATENTS S48,884 Maxim Oct. 29, 1895 1,194,363 Casanovas Aug. 15, 1916 2,383,053 Fanger Apr. 8, 1942 FOREIGN PATENTS 66,446 Denmark Mar. 15, 1948 

